Recently, I struggle with crashing when loading new Object thumbnails, regardless of category. I already checked if there were faulty object files by starting the game multiple times with different folders, but that wasn't the case. The game didn't crash when I gradually loaded thumbnails by adding folders step by step without clearing the Thumbnails cache, but it crashed again when I was loading new Thumbnails in a CC-heavy lot.

Whenever I delete the entire Thumbnails folder, the game is prone to crashing when I have to load new thumbnails, so now I'm not sure when it's convenient to delete Thumbnail cache files. Is it whenever I deleted multiples CCs in one go, or also when I added many new CCs between two gameplays? And should I just load all the Buy Mode thumbnails on an empty lot instead?

If there's no immediate need to delete the thumbnails, you don't need to delete them. They're there to ease up the loading for the various items. You can refresh single thumbnails if needed.

If you just add CC there's no need to delete the thumbnail files. If you remove a small amount of CC it's fine, too. I wouldn't bother unless I had a major cleanup and deleted a whole heap of stuff (lots of redundancy), or added a lot of new defaults and there were too many thumbs to fix for manual refreshing.

It's probably possible to remove thumbnails manually with SimPE, but haven't tested it out on the Thumbnail files. It does work very well with the Cigen file for Bodyshop (but finding the individual files isn't easy if there are a lot of them).

When you delete thumbnails, delete the entire folder instead of just one file. That way, the game copies the thumbs folder over from the install files, and all of the Maxis thumbnails will be there already. Then the game only has to generate your CC thumbnails.
Take it slowly; the first time you browse each catalog, click once to the next page and wait for that to generate before clicking again. If you try to click click click to the end of the catalog, in buy mode or CAS, too quickly then the game will crash as it runs out of memory.

^ only caveat with that one is when you've got a heap of default replacements you want to regenerate thumbnails for, and they show with the old thumbnails instead. You could just regenerate the entire folder to get the maxis ones, and then delete the file you want to fully replace.

@simsample I did remove the entire Thumbnails folder, thus the Maxis ones were preloaded indeed. But my game crashed when I was clicking a random catagory with unloaded thumbnails (e.g Bathroom -> Plumbing), so no quick clicking was involved. But it must be said that I was in a heavy cluttered lot when I was loading those new thumbnails. I yet have to try out in an empty lot.

Update: I still struggle with crashes when loading new thumbnails randomly...

Here's one way you can deal with the thumbnails:

Put in all your mods and CC that you shouldn't remove. Split your CC into chunks (how big each one will be is up to you, but don't do too large chunks). Put in one chunk of CC. Then load up an empty lot in an empty test hood (so you don't accidentally cause any issues with missing CC in your regular hoods). Load in as much of the thumbnails as possible. Go back out of the game. Take out that chunk of CC, put in the next one. Keep going until you've gone through all your CC.

This way you know which thumbnails you've already loaded in (they'll just hang out in the thumbnail files), and you don't overload the system.

@simmer22 yeah that's the method I use right now. However, I tried out the new DXVK because it's supposed to reduce crashes, but that obviously didn't work for me thus I removed it again. So if I can set time aside to start the game, I will try loading thumbnails folder by folder and keep you updated whether or not I can keep crashes upon loading at bay this way.

Update: seems like I've hit the OBJD limit again or something. After removing some objects, no crashing happened upon loading random new thumbnails.

@simsample does it help for you to clear your thumbnails after a major cleanup?

Yes, if you are replacing or removing a lot of content, then you will have a lot of invalid thumbnails. The game will load them into memory each time the game loads, so you're better off removing them and generating a fresh set. Of course regenerating will take a while, but I noticed a big load time improvement when I refreshed caches after I removed a load of CC. Caveat- your mileage may vary depending on your computer and setup.

@Softlism how are you loading thumbnails? Empty lot or cc heavy lot, as you mentioned earlier? I ask because I am thinking that you are crashing not necessarily because of the thumbnails but because of the amount of cc currently in use--like you've hit your object limit. Try this on an empty lot if you haven't already.

I would also make sure that you are adding, never removing cc, unless you aren't going to use it at all anymore. Once you add a section/folder don't remove it. Fix one off thumbnails with Ctrl + Right Click. If the crashing always occurs in the same place--like always when you get to a certain spot in Plumbing Misc, then it's more likely you have a cc issue and a specific item(s) is causing the crashing and you'll need to do a 50/50 until you find it. Honestly this can happen a lot. I've unknowingly had conflicting defaults installed or sometimes some painting or object had an issue and caused crashing. So take note when exactly the crashing happens and if it's random.

Finally, as someone who has loaded a TON of thumbnails, especially in CAS, sometimes there's nothing you can do; the game is just going to crash. I've spent days loading thumbnails before. (I've a 24 GB folder.) Just be patient. Maybe play games on your phone or other device while things load or something. And just continue loading thumbnails from where you left off. Because if it's a game resource issue (and you haven't hit your cc limit), eventually you'll load everything and things will be fine. But if you keep crashing in the exact same spot, then yeah, you'll know it's cc and time to do a 50/50.

@Phantomknight I had the random object crashing issue even on empty lots, but after cutting down on objects meshes, it no longer crashed in Buy/Build mode (at least, if all my thumbnails are already loaded). Today I played the game in Buy/Build Mode in a CC-heavy lot without clearing thumbnails after a cleanup, but no crashing happened, although some pink flashing started to creep up, which is not strange in a CC-heavy lot.

After quitting the game due to pink flashing, I've cleared the Thumbnails for my next play, but if I'm going to reload the objects, I will do that first on an empty lot.

@Softlism good that you were able to play, but you shouldn't need to reload thumbnails everytime you play. I would try to get everything loaded, then play. Only refresh thumbnails if the object is pink in the thumbnail and doesn't show correctly (or blue, which would mean it's missing a mesh). It's your cache files that you should delete every time you play, not your thumbnails.

Update: I've deleted the Thumbnails folder due to the cleanup (and I will wait with deleting that folder again until the next CC cleanup), and reloaded the Buy Mode thumbnails on an empty lot. However, when I switched to a CC-heavy household, pink flashing happened. So I closed the game, removed cigen and group cache only and restarted. No pink flashing on that CC-heavy lot occured.

My takeaway: I have to be more selective with downloading new object meshes, and if I want to do an object haul, I have to delete objects first I won't likely use.